The action of nitric oxide (NO) is considered regulatory in maintaining normal physiological homeostasis in humans and animals, i.e., host-defense, vascular tone, neurotransmission, bronchodilatation and inhibition of platelet function (see Giustarini et al., Clinica Chimica Acta (2003) 330:85-98). NO mediates blood pressure, learning and memory, immune responses, and inflammatory responses (see Thippeswamy et al., Histol. Histopathol. (2006) 21:445-458). In addition, the actions of NO have been observed in pathological conditions such as acute respiratory distress syndrome, hypertension, pulmonary hypertension, arthritis, arteriosclerosis, cancer, diabetes, some neurodegenerative diseases and stroke (see Giustarini et al., Clinica Chimica Acta (2003) 330:85-98).
Traditionally, inhaled NO (iNO) was believed to work exclusively in the lung due to inactivation by hemoglobin (Hb). That is, reaction with oxyhemoglobin to form methemoglobin and nitrate or heme iron nitrosyl hemoblogin (Hb) would cause a loss of vasodilating properties. However it has been found that a stable derivative is formed by a reaction resulting in nitrosylation of a conserved cysteine residue of the β subunit of Hb: S-nitrosylated-Hb (SNO-Hb). This reaction is favored in the presence of oxyhaemoglobin whereas binding of NO to the heme iron is favored in the deoxygenated state. See B. C. Creagh-Brown, et al. (2009) Critical Care 13:212. In the past, remote or non-pulmonary effects of exogenously administered iNO were thought to be undesirable; however, it has recently been found that the stable derivative SNO-Hb retains vasodilatory properties and therefore could be beneficial for circulating targets.
There is clearly a need in the art for improved nitric oxide delivery, particularly systemic delivery that enables delivery of NO, via the circulatory system, to target tissues and organs outside of the pulmonary system.